Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in JAVA):

Solution:
import java.awt.*;
import java.util.*;

public class Main {

    public static void main(String[] args) {
        // write your code here
        Scanner sc = new Scanner(System.in);

        int h = sc.nextInt();
        int w = sc.nextInt();

        String[][] meiro = new String[h][];
        int white = 0;
        for (int i = 0; i < h; i++) {
            meiro[i] = sc.next().split("");
            for (String v: meiro[i]
                 ) {
                if (v.equals(".")) {
                    white++;
                }
            }
        }
        Queue<Point> queue = new ArrayDeque<>();
        queue.add(new Point(0, 0));

        // 上下左右（分岐先）の座標を配列に入れておくと、forループで回して処理できるので便利
        int[] dx = {0, 1, 0, -1};
        int[] dy = {-1, 0, 1, 0};

        int[][] searched = new int[h][w];
        int ans = - 1;
        while (!queue.isEmpty()) {
            Point p = queue.poll();
            if (p.x == w - 1 && p.y == h - 1) {
                ans = searched[p.y][p.x];
                break;
            }
            for (int k = 0; k < 4; k++) {
                int x = p.x + dx[k];
                int y = p.y + dy[k];
                // 分岐先の座標が、2つのif文の条件を満たすなら先頭に追加
                if (x >= 0 && x < w && y >= 0 && y < h) {
                    if (meiro[y][x].equals(".") && searched[y][x] == 0) {
                        searched[y][x] = searched[p.y][p.x] + 1;
                        queue.add(new Point(x, y));
                    }
                }
            }
        }

        if (ans != - 1) {
            ans = white - (ans + 1);
        }

        System.out.println(ans);
    }
}